Unless your computer is just for experimenting you need lots of big hard drives to run that many OS's. You're going to find that you will accumulate software for all those OS's along the way and having that many OS's installed on a single, small drive won't allow you to do much of anything useful since you won't have the drive space for very many apps. Some of us have enough difficulty keeping a single OS uncluttered and running smoothly, having that many installed on one drive is going to compound the difficulties.